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United States Patent |
6,124,035
|
Connell
,   et al.
|
September 26, 2000
|
High temperature transfer molding resins
Abstract
High temperature resins containing phenylethynyl groups that are
processable by transfer molding have been prepared. These phenylethynyl
containing oligomers were prepared from aromatic diamines containing
phenylethynyl groups and various ratios of phthalic anhydride and
4-phenylethynlphthalic anhydride in glacial acetic acid to form a mixture
of imide compounds in one step. This synthetic approach is advantageous
since the products are a mixture of compounds and consequently exhibit a
relatively low melting temperature. In addition, these materials exhibit
low melt viscosities which are stable for several hours at 210-275.degree.
C., and since the thermal reaction of the phenylethynyl group does not
occur to any appreciable extent at temperatures below 300.degree. C.,
these materials have a broad processing window. Upon thermal cure at
.about.300-350.degree. C., the phenylethynyl groups react to provide a
crosslinked resin system. These new materials exhibit excellent properties
and are potentially useful as adhesives, coatings, films, moldings and
composite matrices.
Inventors:
|
Connell; John W. (Yorktown, VA);
Smith, Jr.; Joseph G. (Smithfield, VA);
Hergenrother; Paul M. (Yorktown, VA)
|
Assignee:
|
The United States of America as represented by the Administrator of the (Washington, DC)
|
Appl. No.:
|
310686 |
Filed:
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April 13, 1999 |
Current U.S. Class: |
428/411.1; 428/473.5; 428/524; 528/125; 528/128; 528/170; 528/229; 528/353; 548/473; 548/476 |
Intern'l Class: |
C07D 209/48; C08G 008/02; C08G 073/10 |
Field of Search: |
548/473,476
428/473.5,524,411.1
528/125,128,170,229
|
References Cited
U.S. Patent Documents
5412066 | May., 1995 | Hergenrother et al. | 528/353.
|
5606014 | Feb., 1997 | Connell et al. | 528/353.
|
Primary Examiner: McKane; Joseph
Assistant Examiner: Oswecki; Jane C.
Attorney, Agent or Firm: Hawkins; Hillary W.
Goverment Interests
ORIGIN OF THE INVENTION
The invention described herein was made by employees of the United States
Government and may be manufactured and used by or for the Government or
government purposes without payment of any royalties therein or thereof.
Parent Case Text
CROSS-REFERENCE
This patent application is related to commonly owned co-pending patent
application Ser. No. 09/290295, filed Apr. 13, 1999, entitled
"PHENYLETHYNYL CONTAINING REACTIVE ADDITIVES".
Claims
We claim:
1. An imide compound having the general chemical formula:
##STR4##
wherein Ar represents any aromatic group, wherein PE is radical
represented by
##STR5##
wherein A is a radical selected from the group consisting of O, CO,
SO.sub.2 and
##STR6##
wherein X is selected from the group consisting of substituted aryl group
and unsubstituted aryl group,
wherein R is selected from the group consisting of hydrogen and any
phenylethynyl group represented by --C.tbd.C--X.
2. An imide compound obtained by reacting an aromatic diamine containing
phenylethynyl groups having the general chemical formula
##STR7##
wherein Z is a radical selected from the group consisting of
##STR8##
wherein Ar represents any aromatic group, with any proportion of a
phenylethynyl containing anhydride and a non-phenylethynyl containing
anhydride.
3. A mixture of imide compounds obtained by reacting
3,5-diamino-4'-phenylethynylbenzophenone and any proportion of a
4-phenylethynylphthalic anhydride and phthalic anhydride.
4. The mixture of imide compounds of claim 3, wherein the reaction is
carried out in glacial acetic acid.
5. A process of synthesizing a mixture of imide compounds containing at
least one phenylethynyl group and having the general structural formula
according to claim 1
##STR9##
which process comprises the reaction between
3,5-diamino-4'-phenylethynylbenzophenone and any proportion of a
4-phenylethynylphthalic anhydride and phthalic anhydride.
6. A process of synthesizing a mixture of imide compounds containing at
least one phenylethynyl group and having the general structural formula
according to claim 1
##STR10##
which process comprises the reaction between
3,5-diamino-4'-phenylethynylbenzophenone and any proportion of a
4-phenylethynylpthalic anhydride and phthalic anhydride in glacial acetic
acid.
7. A composite prepared from the imide compound acccording to claim 1.
Description
BACKGROUND OF THE INVENTION
A variety of monomers, oligomers and polymers containing ethynyl
(acetylenic) and substituted ethynyl (i.e., phenylethynyl) groups have
been reported. The ethynyl groups in the polymer are either pendent to the
chain, in the chain or at the chain ends. Many of these materials have
been used to prepare coatings, moldings, adhesives and composites [P. M.
Hergenrother, "Acetylene Terminated Prepolymers" in Encyclopedia of
Polymer Science and Engineering, John Wiley and Sons, New York, Vol. 1, 61
(1985)]. Good processability by either solution casting and/or compression
molding has been observed for the ethynyl and substituted ethynyl
containing materials. In general, thermally cured ethynyl and substituted
ethynyl containing materials exhibit a favorable combination of physical
and mechanical properties. Some ethynyl endcapped materials such as the
Thermid.RTM. resins are commercially available (National Starch and
Chemical Co., Bridgewater, N.J. 08807). Other systems such as acetylene
terminated sulfones have undergone extensive evaluation as matrix resins
[M. G. Maximovich, S. C. Lockerby, F. E. Arnold and G. A. Loughran, Sci.
Adv. Matls. Proc. Eng. Ser., 23, 490 (1978) and G. A. Loughran, A. Wereta
and F. E. Arnold, U.S. Pat. No. 4,131,625, December 1978 to U.S. Air
Force]. Phenylethynyl containing amines have been used to terminate imide
oligomers [F. W. Harris, A. Pamidimuhkala, R. Gupta, S. Das, T. Wu, G.
Mock, Poly. Prep., 24 (2), 325, 1983; F. W. Harris, A. Pamidimuhkala, R.
Gupta, S. Das, T. Wu, G. Mock, Macromol. Sci.-Chem., A21 (8&9), 1117
(1984); C. W. Paul, R. A. Shultz, and S. P. Fenelli, "High Temperature
Curing Endcaps for Polyimide Oligomers" in Advances in Polyimide Science
and Technology, (Ed. C. Feger, M. M. Khoyasteh, and M. S. Htoo), Technomic
Publishing Co., Inc., Lancaster, Pa., 1993, p. 220; R. G. Bryant, B. J.
Jensen, P. M. Hergenrother, Poly. Prepr., 34(1), 566, 1993]. Imide
oligomers terminated with ethynyl phthalic anhydride [P. M. Hergenrother,
Poly. Prepr., 21(1), 81, 1980], substituted ethynyl phthalic anhydride [S.
Hino, S. Sato, K. Kora, and O. Suzuki, Jpn. Kokai Tokyo Koho Japanese
Patent # 63,196,564. Aug. 15, 1988; Chem. Abstr., 115573w, 110, (1989)]
and phenylethynyl containing phthalic anhydrides have been reported. Imide
oligomers containing pendent substituted ethynyl groups [F. W. Harris, S.
M. Padaki, and S. Varaprath, Poly. Prepr., 21(1), 3, 1980 (abstract only);
B. J. Jensen, P. M. Hergenrother and G. Nwokogu, Polymer, 34(3), 630,
1993; B. J. Jensen and P. M. Hergenrother, U.S. Pat. No. 5,344,982 (Sep.
6, 1994)] have been reported. See also J. E. McGrath and G. W. Meyer, U.S.
Pat. No. 4,493,002 (Feb. 20, 1996), J. G. Smith, Jr. Adhesion Society
Proceedings, Vol. 19, 29-32 (1996) and J. W. Connell, J. G. Smith, Jr. and
P. M. Hergenrother, Society for the Advancement of Materials and Process
Engineering Proceedings, Vol. 41, 1102-1112 (1996).
High temperature resins are used in a variety of aerospace and
non-aerospace applications. Generally these materials require high
pressures (>200 psi) to form adhesive bonds, well-consolidated moldings or
fiber reinforced composite laminates. If these systems could be modified
so as to retain the high performance characteristics yet be processable
using resin transfer techniques, then the cost of manuacturing would be
substantially reduced since an autoclave would not be needed.
It is a primary object of the present invention to provide novel
phenylethynyl containing compounds that are processable via resin transfer
techniques. These materials exhibit the proper combination of properties
to allow processing under resin transfer molding conditions. In addition,
upon thermal curing these materials exhibit sufficient thermal stability,
toughness and mechanical properties so as to be useful as adhesives,
coatings, films, filled and unfilled moldings and composite matrix resins
in high performance applications.
Another object of the present invention is to provide novel polymeric
materials that are useful as adhesives, coatings, films, moldings and
composite matrices.
Another object of the present invention is the composition of several new
phenylethynyl containing imide compounds.
SUMMARY OF THE INVENTION
According to the present invention the forgoing and additional objects are
obtained by synthesizing imide compounds containing phenylethynyl groups.
These materials are synthesized by reacting aromatic diamines containing
phenylethynyl groups with various ratios of phthalic anhydride (PA) and
4-phenylethynyl phthalic anhydride (PEPA). These compounds were evaluated
for thermal and rheological properties and for processability. These
materials have advantages over state-of-the-art materials that are
processable by resin transfer techniques, such as epoxies and
bismaleimides in that they have superior thermal stability and can
therefore be used in higher temperature applications.
The unique and unexpected combination of properties exhibited by these
resins includes; ease of synthesis (one-step, quantitative yield
reaction), relatively low melting temperature (.about.182.degree. C.), low
melt viscosity (<1 poise at .about.270.degree. C.), excellent melt
stability (>2 hours at 250-280.degree. C.), high T.sub.g after cure
(>300.degree. C.), excellent thermal stability after cure (no weight loss
after 132 hours at 265.degree. C. in flowing air) and good combination of
mechanical properties after cure (bases on qualitative assessment).
BRIEF DESCRIPTION OF THE DRAWING
For a more complete understanding of the present invention, including its
objects and attending benefits, reference should be made to the
Description of the Preferred Embodiments, which is set forth in detail
below. This Detailed Description should be read together with the
accompanying drawings, wherein:
FIG. 1 is an equation showing the preparation of phenylethynyl reactive
additives according to the present invention.
FIG. 2 is a melt viscosity profile of the uncured powder of
3,5-diamino-4'-phenylethynylbenzophenone (1.0 mole), PA (1.0 mole) and
PEPA (1.0 mole).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
High temperature transfer molding resins (TMR) are prepared from aromatic
diamines containing phenylethynyl groups and various ratios of phthalic
anhydride (PA) and 4-phenylethynyl phthalic anhydride (PEPA) as shown in
the equation of FIG. 1.
In one aspect, the present invention is a mixture of imide oligomers
containing phenylethynyl groups, in any proportion, and consisting of the
general chemical formula
##STR1##
wherein Ar represents any aromatic group, PE is a radical represented by
##STR2##
wherein A is a group comprising O, CO, SO.sub.2 or
##STR3##
X is a substituted or unsubstituted aryl, and R is a hydrogen or any
phenylethynyl group represented by --C.tbd.C--X.
In another aspect the present invention is a process for synthesizing imide
oligomers containing the phenylethynyl group by reacting
3,5-diamino-4'-phenylethynylbenzophenone and any proportion of a
4-phenylethynylphthalic anhydride and phthalic anhydride. By using this
approach where ratios of PA and PEPA are used, a mixture of products is
formed which consequently exhibit a lower melting temperature than that of
the single product obtained by reacting the diamine with either PA or
PEPA. For example, the product obtained from the reaction of
3,5-diamino-4'-phenylethynylbenzophenone and PA in refluxing acetic acid
exhibits a melting point of 278.degree. C. and the product from the same
diamine and PEPA in refluxing acetic acid has a melting point of
252.degree. C. The product from the reaction of this diamine and an
equimolar ratio of PA and PEPA in refluxing acetic acid has a melting
point of 182.degree. C. The lower melting temperature is advantageous in
these systems since it effectively provides a larger processing window
between melting or softening temperature (i.e., onset of flow) and the
temperature of onset of the thermal reaction of the phenylethynyl groups
which rapidly decreases melt flow. The temperature of onset of the thermal
reaction of the phenylethynyl groups (as determined by DSC in a sealed
aluminum pan at a heating rate of 20.degree. C./min) generally occurs
.about.335-350.degree. C. The compounds are prepared in near quantitative
yield in one step by an aromatic diamine containing phenylethynyl groups
with a mixture of a phenylethynyl containing anhydride and a
non-phenylethynyl containing anhydride in refluxing acetic acid. All the
products from this reaction contain at least one phenylethynyl group.
The best results are obtained with the transfer molding material prepared
from 3,5-diamino-4'-phenylethynylbenzophenone (1.0 mole), PA (1.0 mole)
and PEPA (1.0 mole) in refluxing acetic acid (designated TMR-1). Transfer
molding materials prepared from 3,5-diamino-4'-phenylethynylbenzophenone
and different ratios of PA and PEPA, for example, PA (1.5 mole) and PEPA
(0.5 mole) or PA (0.5 mole) and PEPA (1.5 mole) were also prepared
(designated TMR-2 and TMR-3, respectively).
All of above compounds exhibit relatively low melting temperatures. TMR-2
and TMR-3 exhibit two melting transitions by DSC. The onset of the thermal
reaction of the phenylethynyl groups occurred .about.340.degree. C. and
reached a maximum at .about.380.degree. C. After curing for one hour at
350.degree. C. in a sealed aluminum pan, no T.sub.g s were detectable by
DSC. In addition, no residual exothermic transitions or crystalline
melting transitions were detected. This information suggests that after
this thermal cure, these materials had a moderate to high degree of
crosslinking and were fully cured. Thermomechanical analysis (TMA) of a
piece of molding prepared from TMR-1 that had been cured for 1 hour at
350.degree. C. indicated a T.sub.g of .about.320.degree. C.
Thermogravimetric analyses (TGA) of uncured imide powders of these
materials indicated temperatures of 5% weight loss of .about.500.degree.
C. in air and .about.525.degree. C. in nitrogen. These results are
comparable to those typically exhibited by aromatic polyimides. Isothermal
gravimeteric analysis (ITGA) of a piece of molding prepared from TMR-1 and
cured for one hour at 350.degree. C. in air indicated no weight loss after
132 hours at 265.degree. C. in flowing air. ITGA performed on this molding
at 350.degree. C. in air indicated a 50% weight loss after 132 hours in
flowing air. For comparative purposes, a phenylethynyl terminated imide
oligomer with a number average molecular weight of 5000 g/mole exhibited a
10% weight loss after 132 hours at 350.degree. C. in air [See J. A.
Hinkley and B. J. Jensen, High Perf. Polym. Vol. 7, 1-9 (1995)].
In addition, melt rheology was performed on the uncured powder of TMR-1.
The material was heated to .about.210.degree. C. and exhibited a complex
melt viscosity of .about.10 poise. There was no change in the complex
viscosity after a one hour hold at this temperature. The material was
subsequently heated to 350.degree. C. over an additional 2 hour period.
The complex melt viscosity decreased to less than 1.0 poise at
.about.240.degree. C. and to 0.1 poise at .about.270.degree. C. The
complex melt viscosity did not increase until the temperature reached
.about.325.degree. C. corresponding to a time of .about.2.5 hours after
the material was first heated to 210.degree. C. A graph of the melt
viscosity versus temperature and time is presented in FIG. 2.
Having generally described the invention, a more complete understanding
thereof can be obtained by reference to the following examples, which are
provided herein for purposes of illustration only and do not limit the
invention.
Synthesis of Transfer Molding Resins (TRMs)
EXAMPLE 1
Synthesis of TRM-1 from 3,5-diamino-4'-phenylethynylbenzophenone (1.0
mole), phthalic anhydride (1.0 mole) and 4-phenylethynylphthalic anhydride
(1.0 mole)
Into a 3 L three-necked round-bottom flask equipped with a mechanical
stirrer, thermometer and reflux condenser was placed
3,5-diamino-4'-phenylethynylbenzophenone (187.4 g, 0.60 mole), phthalic
anhydride (88.9 g, 0.60 mole), 4-phenylethynylphthalic anhydride (148.9 g,
0.60 mole) and glacial acetic acid (785 mL, 34% solids). The mixture was
heated to reflux (.about.120.degree. C.) to give a dark brown solution.
After .about.2 hours at this temperature a large amount of light tan
precipitate formed making stirring impossible. Heating was continued for 1
additional hour and the reaction mixture was cooled to room temperature.
The product was isolated by filtration and washed three times in warm
water to remove residual acetic acid. The solid was air dried overnight
and most of the next day and subsequently placed in a forced air oven at
125.degree. C. overnight. The light tan powder (397 g, 98% of theoretical
yield), exhibited a melting transition at .about.182.degree. C., and an
exothermic transition due to the thermal reaction of the phenylethynyl
groups beginning at 346.degree. C. and peaking at 381.degree. C. as
determined by DSC. The heat of reaction was .about.275 J/g.
EXAMPLE 2
Synthesis of TRM-2 from 3,5-diamino-4'-phenylethynylbenzophenone (1.0
mole), phthalic anhydride (1.5 mole) and 4-phenylethynylphthalic anhydride
(0.5 mole)
Into a 500 mL three-necked round-bottom flask equipped with a mechanical
stirrer, thermometer and reflux condenser was placed
3,5-diamino-4'-phenylethynylbenzophenone (23.43 g, 75.0 mmole),), phthalic
anhydride (16.66 g, 112.5 mmole), 4-phenylethynylphthalic anhydride (9.31
g, 37.5 mmole) and glacial acetic acid (125 mL, 30% solids). The mixture
was heated to reflux (.about.120.degree. C.) to give a dark brown
solution. After .about.2 hours at this temperature a large amount of light
tan precipitate formed making stirring impossible. Heating was continued
for 1 additional hour and the reaction mixture was cooled to room
temperature. The product was isolated by filtration and washed three times
in warm water to remove residual acetic acid. The solid was air dried
overnight and subsequently placed in a forced air oven at 130.degree. C.
for six hours. The light tan powder (45.0 g, 96% of theoretical yield),
exhibited a melting transition at .about.179.degree. C. and 235.degree.
C., and an exothermic transition due to the thermal reaction of the
phenylethynyl groups beginning at 346.degree. C. and peaking at
383.degree. C. as determined by DSC. The heat of reaction was .about.209
J/g.
EXAMPLE 3
Synthesis of TRM-3 from 3,5-diamino-4'-phenylethynylbenzophenone (1.0
mole), phthalic anhydride (0.5 mole) and 4-phenylethynylphthalic anhydride
(1.5 mole)
Into a 500 mL three-necked round-bottom flask equipped with a mechanical
stirrer, thermometer and reflux condenser was placed
3,5-diamino-4'-phenylethynylbenzophenone (21.98 g, 70.4 mmole), phthalic
anhydride (5.21 g, 35.2 mmole), 4-phenylethynylphthalic anhydride (26.20
g, 105.5 mmole) and glacial acetic acid (200 mL). The mixture was heated
to reflux (.about.120.degree. C.) to give a dark brown solution. After
.about.2 hours at this temperature a large amount of light tan precipitate
formed making stirring impossible. Heating was continued for 1 additional
hour and the reaction mixture was cooled to room temperature. The product
was isolated by filtration and washed three times in warm water to remove
residual acetic acid. The solid was air dried overnight and subsequently
placed in a forced air oven at 130.degree. C. for six hours. The light tan
powder (50.2 g, 99% of theoretical yield), exhibited a melting transition
at .about.191.degree. C. and 230.degree. C., and an exothermic transition
due to the thermal reaction of the phenylethynyl groups beginning at
340.degree. C. and peaking at 374.degree. C. as determined by DSC.
While the invention has been described in terms of its preferred
embodiments, those skilled in the art will recognize that the invention
can be practiced with modification within the spirit and scope of the
appended claims.
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